(a) Field of the Invention
The present invention relates to a cryocooler with variable compressions depending on variations in load, and more particularly to a cryocooler with variable compressions, which the compressions are actively varied depending on load variations and setup temperature control information.
(b) Description of the Related Art
In a general, a cryocooler to be used in aerospace needs to have minimum power consumption since its operation has to last for a long time in astrospace. The cryocooler requires high cooling ability at its initial operation, but if it reaches to some extent a required temperature and cooling ability as times goes on and thus a temperature of a cooling section becomes lowered, the cooling ability required for keeping such a state is not high. Nevertheless, if the cooling operation is constantly continued, it is wasteful power consumption.
Accordingly, under the condition that required cooling ability is varied depending on variations in load, it is important to reduce the wasteful power consumption and secure the life of the cryocooler by gradually lowering the cooling ability when the cryocooler reaches a certain state.
To make the cooling ability of the cryocooler be variable, a driving cycle of a compressor may be adjusted, or compressing pressure may be adjusted in accordance with change in a stroke of a piston, or an inertance tube variable in length may be adjusted to have a required length. With this configuration, the wasteful power consumption is reduced to thereby increase power efficiency, and one system is enough to cover a variety of cooling ability to thereby increase utilization.
Although the cooling ability is varied due to change in operation flux and compression pressure when the compression cycle or the piston displacement is adjusted by changing a motor operation cycle of a linear motor for driving the compressor, such variation is difficult to find out an optimal point because of a matching problem between a pulse tube and the inertance tube, thereby decreasing efficiency. That is, it is difficult to deal with sizes varied depending on the respective cycles. Also, there is a limit since various changes in the length of the inertance tube are impossible.